Fabric tensioning mechanisms for use in circular knitting machines



Jan. 8, 1963 J. R. coMAs 3,071,948 FABRIC TENSIONING MECHANISMS FOR USE IN CIRCULAR KNITTING MACHINES Filed May a, 1959 INVE N United States The present invention-relates to improvements in the fabric tensioning mechanisms for use in circular knitting machines which manufacture separate or individual knitted articles such as stockings, that is to say, those machines in which knitting starts on bare needles for each article, and when the last course of loops has been completed at the opposite end of the said article the latter is released from the machine needles and ejected to a collecting spot or container wherein the separate articles are received.

In the machines of the above referred kind, it is neces sary to impart some tension to the fabric being knitted with the purpose of maintaining a constant tensioning of the loops throughout the length of the article and to ensure other important features of the end product.

For this purpose a tensioning device has been-already suggested consisting in a tensioning weight provided with a clamp device which includes a cup shaped member and a. cover shaped member engageable with the opening of the former, both arranged coaxially and longitudinally slidable the one with respect to the other, so that the cover member may be engaged with the opening of the cup member, theend of the article being formed being clamped between both members in order to subject it to the weight of the tensioning device.

Both the members constituting the clamp device are mounted in a freely revolving arrangement as regards the tensioning weight so that they are made to rotate by the rotation of the fabric tube being formed, which rotation is caused by the turning of the machine needle cylinder. A mechanism, the description of which is not necessary for the actual purposes of the present invention, is charged with raising the ensemble of the weight and clamp device to the height Where the machine needles work, in order to take the end of a new article every time a knitting operation is to be started.

When articles made of very fine gauge yarn are to be knitted, such as nylon stockings, it is of paramount importance to prevent by any means that the knitted fabric tube be subjected to the slightest torsioning stress in order to avoid wrinkles which could lead to the rejection of the completed stocking. Thence, with the use of the tensioning mechanisms of the above referred kind, even when universal joint devices in the mounting of the two members of the clamp device and the best bearings ensuring the rotation thereof with the least possible friction, are used, it is not possible to avoid some resistance to the rotation which results in a corresponding torsion of the knitted fabric tube. On the other hand, these mechanisms, when in the upper portion of the traverse thereof, are under the action of air jets generally used to facilitate the entry of the fabric into the clamp device, which jets cross the working zone where the loops are formed, and therefore the mechanisms are very prone to linter accumulation which tends to block the bearings or to increase the. friction thereof, so that the feared torsion in fact takes place at the least forgetfulness of the operator.

The object of the invention is, therefore, to provide improvements in the tensioning mechanisms of the above kind, by means of which the knitted fabric tube, tensioned between the needles of the machine cylinder and the tensioning device imparting tension thereto is never subjected to torsional stresses which might give rise to the above 'atent O F 3,071,948 Patented Jan. 8, 1963 drawbacks, and for this purpose the improvement consists in connecting at least one of the members of the tensioning mechanism clamp device with a driving means which positively rotates the clamp device synchronously with the machine cylinder, so that this clamp device sets the lower end of the article being formed in rotation synchronously with the cylinder and the said article is released from the torsional action necessary for rotating the clamp device.

The tensioning mechanism incorporating the above improvement provides a great deal of advantages over the known mechanisms as seen directly in the actual performance of the machines, amongst which are to be found:

(1) Avoids the torsional jerks occurring on the article being formed when the machine is stopped or set into motion, to surpass the inertia of the tensioning mechamsm.

(2) Prevents tension uneveness of the loops when the machine is knitting in reciprocating motion, as in such working conditions the clamp device of the tensioning mechanism remains in a stationary intermediate position and the article is alternatively twisted and untwisted in both directions so that the loops located towards the ends of the reciprocating traverse are longer than the central loops.

(3) Prevents tension uneveness in the article as produced by the small, but in fact present, torsion which is necessary to drive the clamp device and which, in practice, continuously changes according to the instant friction which the bearings of this device encounter.

The cover of the clamp device preferably is made fast to a supporting rod mounted for rotation on the body of the tensioning device, and this rod is connected by means of a suitable gearing with a movable part of the machine, so that the cover member is made to revolve synchronously with the machine cylinder, and when engaged with the cup member of the same device, with the fabric clamped therebetween, it draws the latter in rotation owing to the fact that the cup member is freely revolving as regards the rod.

According to a preferred embodiment of the invention the cover member supporting rod of the clamp device has fastened thereto a toothed gear meshing with a pinion mounted for rotation on bearings provided in the body of the tensioning weight, but prevented from axially moving as regards the same, the said pinion being provided with an axial bore wherein one vertical guide for the tensioning weight may slide, and with means connecting the same in sliding relation with the said guide which, in turn, is mounted for rotation in supports fast to the machine and connected with a member of the latter performing a synchronous motion as regards the needle cylinder.

In order to facilitate the discussion a sheet of drawings is joined to the present specification wherein a diagrammatic embodiment of a tensioning mechanism incorporating the present improvements in one of the possible forms, has been shown only by way of example not restrictive of the scope of the invention.

In the drawing, the single FIGURE is a side elevational view of the mechanism in question, partially in cross section.

In the FIGURE the reference characters 10 and 11 show the two vertical rods constituting the sliding guides for the ensemble of the tensioning weight. The latter comprises a rectangular supporting frame 12 having parallel vertical sections 13 and 14 adjacent to the rods 10 and 11, and horizontalsections 15 and 16 connecting the upper and lower ends of the former, respectively.

The vertical section 13 is formed with a lateral extension 17 having a vertical bore 18 wherein the guide bar 10 is snugly received. A sleeve 19 is mounted into the bore 18 and snugly surrounds the said rod for the purpose to be described in detail thereafter. As it may be seen this sleeve constitutes one of the sliding members of the tensioning mechanism along the rod 10.

The lower, horizontal section 16 of the frame 12 extends towards the opposite side of the latter and is split in a fork the legs 20 of which are located at both sides of the guide rod 11, thereby constituting the other guide member for the vertical sliding of the tensioning weight.

The horizontal section 15 of the frame 12 has a wide opening 21 at the central part thereof and the bearing 22 is secured at the upper part thereof by means of the flange 23 of the bearing and the screws 24. The tubular rod 25 is mounted in fitted and freely slidable relation in the said bearing 22 and extends upwardly; it has fastened, at an intermediate height, the conventional devices for imparting thereto vertical motions for opening and closing the clamp device 26 which will be described hereafter. These devices are embodied by the parts 27.

The upper end of the tubular rod 25 is formed with a thread 28 and close to the latter there is a small radial shoulder 29, the inner race of the ball bearing 30 being fastened between the thread and shoulder by means of the terminal nut 31. The outer race of the said bearing is made fast by means of the circlip 32 at the bottom of the box 33 formed at the lower part of the cup member 34 of the clamp device 26.

A supporting rod 35 is guided in sliding and rotating relation within the tubular rod 25 and protrudes from the lower end of the latter. The rod 35 is guided to revolve, but prevented from vertical displacement relative to frame 12, by means of the ball bearing 36 mounted in the opening 37 which is suitably centered in the lower section 16 of the frame 12.

The upper end of rod 35 protrudes within the cup member of the clamp device 26 and terminates in a thread 37, with which a corresponding thread formed in the central hole 38 of the cover member 39 of the said clamp device, engages.

The associated edges of members 34 and 39 have the conventional recessed construction, shown at 40, in order to securely fasten the formed fabric 41.

The operation of the mechanism for fastening and releasing the article is conventional: Before starting the knitting operation an automatic mechanism of the machine, not shown, raises the ensemble of the described tensioning weight until the clamp device reaches the needle level in the machine cylinder. The cup member of the clamp device, for example, abuts with a salient portion of the cylinder inside, and with continued raising of the mechanism ensemble, the frame 12 and inner rod 35 slide upwardly as regards the tubular rod 25 which has stopped along with the tubular member 34, so that the cover member moves upwardly from the said cup member thereby leaving between it and the cup member room enough for allowing entrance into the latter of the fabric which begins to be formed. When the fabric formation has proceeded in the sufficient amount for becoming suitably inserted within the cup member, the above automatic mechanisms allow the lowering of the ensemble of the tensioning weight so that, of course, in the first place the clamp device is closed because the spring 42 tends to apply the cover member against the cup member, and when the said members reach the illustrated position With the fabric clamped therebetween, the ensemble of the tensioning weight becomes freely suspended from the knitted fabric tube thereby imparting to the same the suitable working tension.

For releasing the completed article when the ensemble has reached the lower portion of its traverse, an oscillating lever, not shown, operated by the automatic mechanisms of the machine, pushes downwardly the parts 27 thereby causing the tubular rod 25 and cup member 34 to move downwards. The rod 35 and cover member 39 remain stationary because of the frame abutting in a suitable stop. The members 34 and 39 move apart from one another and permit the article to be withdrawn by any suitable means.

The revolving rod 35 protrudes downwardly from the frame 12 and has fastened rigidly thereto a toothed wheel 43 the toothed periphery of which is located adjacent to the guide rods 10, 11. The sleeve 19 protrudes also downwardly from the extension 17 and terminates in a pinion 44 having a toothing corresponding to that of the former wheel and meshing therewith.

The sleeve 19, which is adapted to rotate within the bore 18, is prevented from axial displacement with respect to the latter by being formed with a peripheral groove 45 of square cross section wherein the terminal tenon 46 formed in the screw 47 is received, the screw being received in a suitably threaded radial hole formed in the wall of the extension 17.

On the other hand the sleeve 19 has a radial pin 48 protruding in the inside thereof and engaging in the longitudinal groove 49 formed throughout the length of the rod 10 over which the said sleeve 19 slides.

Finally the rod 10 is supported in terminal bearings, not shown, so that it may freely revolve and it is imparted a rotation movement synchronous with that of the machine needle cylinder, with a speed such that the step down gears 4443 cause the rod 35 and clamp device 3439 to rotate with the same angular velocity as the machine cylinder, owing to the fact that the cup member 34 is driven through the engagement thereof with the cover member 39, with the fabric interposed therebetween. Thus, as the said clamp device truly follows the movement of the needle cylinder and formed fabric tube, the latter never can be subjected to the slightest torsion which could damage it.

Although what is described above specifically applies to the preferred embodiment, it will be understood that the above mechanism may be developed in other manners which likewise will fall Within the scope of the invention. For example, instead of operating the cover member 39 by making the rod 35 rotatable, the latter may remain stationary and the cover member be arranged in freely revolving relation at the end thereof as in the usual constructions, and at the same time the cup member may be fastened to the end of the tubular rod 25 and the latter may be driven in a similar manner, account having had to the suitable detail modifications. It is, thus, also possible simultaneously to operate both members of the clamp device, where some slippage between the article and driven member could be foreseen.

In the same manner the arrangement of the sleeve 19 in the bore 18, and also the engagement thereof with the guide and drive rod 13 has only been described in 9. diagrammatic manner showing the operation principle. In the design of members any such fixtures or constructions leading to the performance of this engagement with a minimum friction in order that the lateral reaction of the pin 48 against the edge of the groove 49 does not cause a noticeable slowing down of the ensemble of the tensioning weight, may, of course, be used in practice. For example, ball bearings may be used between the sleeve '19 and the housing 19 thereof, as well as between the said sleeve and groove 49, such as a circulating ball device.

Neither is it absolutely necessary in accordance with the invention that the drive of the rods 25 or 35 be performed through the rod 10. This embodiment has only been cited by way of example, for convenience of the transformation operated in order to test the invention in an existing machine, but, of course, this drive may also be performed by means of an independent rod as regards the guides lit and 11, in particular for some application cases wherein the ensemble of the tensioning weight freely hangs from the fabric tube with no other connection with the machine. In lieu of a revolving vertical rod, a flexible transmission may also be used, for example.

Finally, the connection point of the driving means, either the rod or another, or a flexible transmission, to the machine mechanisms, may also be selected in accordance with the constructive conveniences, provided that'the movement obtained at the clamping device is identical with that of the needle cylinder.

In certain instants within the article formation cycle, for example in the clamping stage of the latter, when starting the knitting, and at the end of the cycle for releasing and ejecting the article, it may be desirable to discontinue rotation of the clamp device in order to facilitate these operations, in which case the gearing connecting the said clamp device with the point from which the drive is taken may include a conventional clutch device, controlled by the automatic mechanisms of the machine, which starts and stops the clamp device at the suitable moments.

In some special cases it may also be necessary, for example to provide for some slippage occasionally occurring between the end of the article and the clamp device, it may also be necessary to alter the timing or the speed of the same as regards the cylinder, and in view of this the gearing may incorporate a speed variator to be controlled by hand or thru the machine automatic movements.

Other Variations such as shape and size, as well as suitable materials, may also be used in the present invention without departing from the scope thereof as defined by the appended claims.

I claim:

1. In a fabric take-up mechanism for a circular knitting machine having a rotary needle cylinder which turns about its own axis, in combination, a combined weight and clamp assembly adapted to be clamped to the fabric during the knitting thereof for applying the force of theweight thereto, said assembly including a clamping means which is adapted to be clamped to the knitted fabric during the knitting of an elongated tube of fabric; elongated guide means having at least one guide rod whose axis remains stationary and guidingly engaging said assembly to guide the same for movement along the axis of the needle cylinder during the knitting of a tube of fabric, said guide rod extending parallel to the axis of the needle cylinder; and drive means operatively connected with said clamping means for turning the latter in synchronism with the needle cylinder so as to prevent any torsion in the loops of the knitted fabric.

2. In a fabric take-up mechanism for a circular knitting machine having a rotary needle cylinder adapted to turn about its own axis, in combination, a pair of elongated parallel guide rods respectively having axes which are stationary and which are adapted to extend parallel to the axis of the needle cylinder; weight means located between and guided by said guide rods for movement along said axis of the needle cylinder; clamp means turnably connected to said weight means for free rotation with respect thereto about the axis of the needle cylinder, said clamp means being adapted to be clamped onto the tube of knitted fabric to apply thereto the tension provided by said weight means; and drive means cooperating with said clamp means for turning the latter about the axis of the needle cylinder in synchronism therewith.

3. In a fabric take-up mechanism for a circular knitting machine having a rotary needle cylinder which turns about its own axis, in combination, a pair of elongated parallel guide rods at least one of which remains stationary at all times, said guide rods respectively having axes which are adapted to extend parallel to the axis of the needle cylinder; weight means cooperating with said guide rods to be guided by the latter for movement along the needle cylinder axis; clamp means adapted to be clamped onto a tube of knitted fabric during the knitting thereof, said clamp means being connected with said weight means for free rotation with respect thereto about the axis of the needle cylinder so that said clamp means serves to suspend the weight means from the tube of fabric to provide on the latter a suitable tension; and drive means cooperating with said clamp means for rotating the latter synchronously with the needle cylinder.

4. In a fabric take-up mechanism for a circular knitting machine having a rotary needle cylinder which turns about its own axis, in combination, a pair of guide rods which extend parallel to each other and which respectively have axes which are adapted to extend parallel to that of the needle cylinder, one of said guide rods being stationary and the other of said guide rods being turnable about its own axis; Weight means located between and guided by said guide rods for movement along the axis of the needle cylinder; clamp means adapted to be clamped onto a tube of fabric during the knitting thereof, said clamp means carrying said weight means and being connected to the latter for free rotation with respect thereto about the axis of the needle cylinder; and transmission means cooperating with said other guide rod and with said clamp means for transmitting rotation of said other guide rod about its own axis to said clamp means for rotating the latter synchronously with the needle cylinder to prevent any torsion in the loops of-the knitted fabric.

5. In a fabric take-up mechanism for a circular knitting machine having a rotary needle cylinder adapted to turn about its own axis, in combination, a pair of elongated parallel guide rods adapted to extend parallel to the axis of the needle cylinder, one of said rods being stationary and the other of said rods being rotatable about its own axis; weight means located between said rods and guided thereby for movement along the axis of the needle cylinder; a pinion connected to said rotatable guide rod for rotary movement therewith while being freely movable longitudinally thereof, said weight means cooperating with said pinion for shifting the latter along said rotatable guide rod together with said weight means; an elongated drive rod extending along the axis of said needle cylinder coaxially therewith and guided for rotation about its axis by said weight means, said rod extending upwardly beyond said weight means; clamp means located over said weight means and connected to said drive rod for rotation therewith, said clamp means being adapted to be clamped onto a tube of knitted fabric during the knitting thereof for applying to the fabric the weight of said weight means for tensioning the fabric during the knitting thereof, said drive rod and weight means being axially immovable one with respect to the other; and a gear fixed coaxially to said drive rod and meshing with said pinion to be driven by the latter during rotation of said other guide rod, the speed of rotation of said rotatable guide rod and the transmission ratio of said pinion and gear providing said drive rod and clamp means with a rotation which is synchronous with the rotation of the needle cylinder to prevent any torsion in the loops of the knitted fabric.

6. In a fabric take-up mechanism for a circular knitting machine which has a rotary needle cylinder turnable about its own axis, in combination, a pair of parallel guide rods adapted to extend parallel to the axis of the needle cylinder, one of said guide rods being stationary and the other of said guide rods being turnable about its own axis; a pinion axially slidable along said other guide rod but being rotatable therewith; weight means located between and guided by said guide rods for movement along the axis of the needle cylinder, said Weight means cooperating with said pinion to shift the latter along said rotatable guide rod with said weight means; an elongated drive rod coaxial with the needle cylinder and guided for rotation by said weight means and being axially immovable With respect thereto, said drive rod extending upwardly beyond said weight means; a guide sleeve through which said drive rod slidably extends to be guided in part by said sleeve for rotary movement, said sleeve being axially movable with respect to said weight means; a clamping cup member having an open top and being connected to said sleeve for free rotary movement with respect thereto while being axially immovable with respect to said sleeve; a clamping cover adapted to close the top of said clamping cup and fixed to said drive rod; spring means cooperating with said sleeve for urging the latter together with said cup toward said cover member for clamping a tube of knitted fabric between said cup and cover member; and a gear fixed coaxially to said drive rod and meshing with said pinion so that said drive rod together with said clamping cover member and together with said clamping cup member which frictionally turns with said cover member as a result of said spring means rotate in response to rotation of said rotatable guide rod, the speed of rotation of the latter and the transmission ratio of said pinion and gear providing said clamping member with a rotary movement which is synchronous with the rotation of the needle cylinder so as to prevent any torsion in the loops of the knitted fabric.

7. In a fabric take-up mechanism for a circular knitting machine having a rotary needle cylinder adapted to turn about its own axis, in combination, elongated guide means extending parallel to the axis or" the needle cylinder; weight means engaging said guide means and guided by said guide means for movement along the axis of the needle cylinder, said weight means being held against rotation; clamp means turnably connected to said Weight means for free rotation with respect thereto about the axis of the needle cylinder, said clamp means being adapted to be clamped onto the tube of knitted fabric to apply thereto the tension provided by said weight means; and drive means cooperating with said clamp means for turning the latter about the axis of the needle cylinder in synchronism therewith.

References Cited in the file of this patent UNITED STATES PATENTS 2,694,304 Butler NOV. 16, 1954 

1. IN A FABRIC TAKE-UP MECHANISM FOR A CIRCULAR KNITTING MACHINE HAVING A ROTARY NEEDLE CYLINDER WHICH TURNS ABOUT ITS OWN AXIS, IN COMBINATION, A COMBINED WEIGHT AND CLAMP ASSEMBLY ADAPTED TO BE CLAMPED TO THE FABRIC DURING THE KNITTING THEREOF FOR APPLYING THE FORCE OF THE WEIGHT THERETO, SAID ASSEMBLY INCLUDING A CLAMPING MEANS WHICH IS ADAPTED TO BE CLAMPED TO THE KNITTED D FABRIC DURING THE KNITTING OF AN ELONGATED TUBE OF FABRIC; ELONGATED GUIDE MEANS HAVING AT LEAST ONE GUIDE ROD WHOSE AXIS REMAINS STATIONARY AND GUIDINGLY ENGAGING SAID ASSEMBLY TO GUIDE THE SAME FOR MOVEMENT ALONG THE AXIS OF THE NEEDLE CYLINDER DURING THE KNITTING OF A TUBE OF FABRIC, SAID GUIDE ROD EXTENDING PARALLEL TO THE AXIS OF THE NEEDLE CYLINDER; AND DRIVE MEANS OPERATIVELY CONNECTED WITH SAID CLAMPING MEANS FOR TURNING THE LATTER IN SYNCHRONISM WITH THE NEEDLE CYLINDER SO AS TO PREVENT ANY TORSION IN THE LOOPS OF THE KNITTED FABRIC. 